The invention provides a standup assisting device capable of obtaining an initial standup lifting force by a gas spring even in a closed state of a seating portion, and realizing a thin thickness. A seat has a seat portion on which a top plate and a bottom plate are swingably supported, a swing mechanism housed in the seat, and locking means for closing the seat. It is a standing-up assisting device which assists the standing of a person who is seated on the seating section by tilting the upper surface plate by the mechanism, and the swinging mechanism is at least a gas spring which the piston rod supported on the pivot shaft projects to open the seating section. An offset member in which at least one of the one end and the other end of the gas spring is offset so that the axis of rotation of the rotation axis and the axis of emergence of the piston rod orthogonal to the axis of rotation do not intersect in the same plane Is supported by the pivot shaft. [Selected figure] Figure 1【課題】着座部を閉状態であってもガススプリングによる初期起立持ち上げ力を得ることができ、薄い厚みを実現できる起立補助装置を提供する。【解決手段】上面板と底面板とが揺動自在に支持された着座部と、着座部に収納された揺動機構と、着座部を閉状態にするロック手段と、を有し、揺動機構により上面板を傾斜して着座部に着座した人の起立を補助する起立補助装置であり、揺動機構は、回動軸に支持されたピストンロッドが突出して着座部を開くガススプリングを少なくとも備え、ガススプリングの一端と他端の少なくとも一方は、回動軸の回動軸芯と回動軸芯に直交するピストンロッドの出没軸芯とが同一平面上で交差しないようにオフセットするオフセット部材を介して回動軸に支持される。【選択図】図１
